Compression of single-crystal magnesium oxide to 118 GPa and a ruby pressure gauge for helium pressure media
- NWU
The pressure-volume equation of state (EoS) of single-crystal MgO has been studied in diamond-anvil cells loaded with helium to 118 GPa and in a non-hydrostatic KCl pressure medium to 87 GPa using monochromatic synchrotron X-ray diffraction. A third-order Birch-Murnaghan fit to the non-hydrostatic P-V data (KCl medium) yields typical results for the initial volume, V{sub 0} = 74.698(7) {angstrom}{sup 3}, bulk modulus, K{sub T0} = 164(1) GPa, and pressure derivative, K' = 4.05(4), using the non-hydrostatic ruby pressure gauge of Mao et al. (1978). However, compression of MgO in helium yields V{sub 0} = 74.697(6) {angstrom}{sup 3}, K{sub T0} = 159.6(6) GPa, and K' = 3.74(3) using the quasi-hydrostatic ruby gauge of Mao et al. (1986). In helium, the fitted equation of state of MgO underdetermines the pressure by 8% at 100 GPa when compared with the primary MgO pressure scale of Zha et al. (2000), with K{sub T0} = 160.2 GPa and K' = 4.03. The results suggest that either the compression mechanism of MgO changes above 40 GPa (in helium), or the ruby pressure gauge requires adjsutment for the softer helium pressure medium. We propose a ruby pressure gauge for helium based on shift of the ruby-R{sub 1} fluorescence line ({Delta}{lambda}/{lambda}{sub 0}) and the primary MgO pressure scale, with P (GPa) = A/B{l_brace}[1 + ({Delta}{lambda}/{lambda}{sub 0})]B - 1{r_brace}, where A is fixed to 1904 GPa and B = 10.32(7).
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006950
- Journal Information:
- Am. Mineral., Vol. 93, Issue (11-12) ; 2008; ISSN 0003-004X
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Crystal structure of hydrous wadsleyite with 2.8% H[subscript 2]O and compressibility to 60 GPa
On the Elastic Behaviour of Zeolite Mordenite: a Synchrotron Powder Diffraction Study